You can use the embed code of the form to add it to your website, it is not necessary for you to download and host the source code. You can also create a link from your website to open up your form created with JotForm, this can be done by using the href tag.

I will be building my own website with WIX. Do you offer a code or form for my customers to upload their own designed ad for me to publish in my newspaper? If so what form would I use to be compatiable with WIX?